Thursday, 5 November 2015

Dellcade Compact Arcade Machine Build Part Two: Ones and Zeros

Initially, I planned to mount the Raspberry Pi up against the back plate so that the external leads would connect directly to the Pi, which would have been convenient . However, I decided to use short 300 mm extensions for HDMI, USB and Network to allow the Pi to be mounted with more flexibility inside the enclosure.

The first instalment of the Dellcade compact arcade machine can be seen here...

Designing the I/O rear panel, ones and zeros.

The panel was created using 1.6 mm aluminium sheet I had lying around this, was cut with a non ferrous saw blade on a chop saw.

The disc sander made short work of forming a neat radius on the corners. It is a versatile tool, in most respects, you can forego using a band saw for a large disc or belt sander.

For the small holes I used an optical centre punch. Once you have used one there's just no going back... if you like precision that is! In the majority of my projects, I tend to utilise it, even for home etching PCB drilling particularly, if one of the components needs to be a close tolerance.

Accurate alignment!

The enclosure back panel was first pre drilled, then, using a bearing guided router bit the rebate was cut to the required depth - just enough to leave a shadow line when the aluminium plate was installed. With time and gained experience you can do just about anything with a router.

LG Hi-MACS or some other types of composite are too brittle to form a tapped hole so, I decided that I'd use M3 blind rivet nuts or rivnuts extensively thought out the project (in this instance for fixing the rear panel as an alternative for expensive press fit brass inserts). Rivet nuts are intended to be expanded thus, grip the material by using a special tool. If you drill a precise hole and counter sink for a flush fit you can push fit them or use a dab of epoxy (there is a small lip on the rear of the rivet nut, this will stop it being pulled through the hole).

This became the desired layout...

Creating clean rectangular holes using a file took the majority of the time here.

*Note-

When filing square holes they can become parallelograms really quick. Make sure your eye line is level with the hole to be filed also, have plenty of natural light.

Try not to file using a sawing action but with one smooth clean pass then, lift the file and repeat.

Stay away from the corners until you are happy with how the hole is forming. After practice, you can actually leave a small radius in the corners which will give a more professional look, as if the hole was stamped out.

Luckily I was spot on the first go!

The Playfield

The main analogue interface of any arcade machine...

The playfield base was a relatively large piece measuring 320 mm x 260 mm. Prior to the actual design a plywood test playfield was constructed to ensure the buttons and joystick were in a comfortable position. These were then measured, normalized and transferred to the CAD design. The hole positions were derived roughly to match the Razor Atrox with a few personal tweaks.

In reality, for a basic MAME based arcade cabinet, unless you enjoy games such as Street Fighter, six or more buttons could be too much.

Yet more rivet nut holes...

I had been hoarding the above speaker grills for quite some years, I knew they would come in ;)

Perspex Playfield

Cabinet graphics can really bring any arcade machine to life so, I decided early in the design process, that I would implement a perspex play field top thus I could then use a custom graphics underlay.

The playfield was constructed using 3mm polycarbonate though, I would advise the use of acrylic as it is more resistance to scratching and polishing marks. Acrylic also drills and machines much better! Polycarbonate tends to be stringy when drilling and can gum up the cutter or drill bit.

A quick rub around with a chamfer router bit gave the illusion that the speaker grills were not as recessed as they actually were.

Again... a bearing guided 45 degree chamfer router bit was used to soften the edges for aesthetics and comfort.

Perspex Graphic

The graphics were mostly created in Adobe Illustrator by firstly exporting the Perspex outline from Solidworks in DXF format and then importing them directly into Illustrator to maintain 1:1 scale.

Unfortunately, I do not own a A3 printer so the graphic design had use an A4 footprint. Luckily, the base panel colour was black so any discrepancies would not been seen under the perspex. For cutting of the holes, a compass cutter came in very handy!

With the protective coating removed, the eight fixing holes were then countersunk flush with the perspex. The NOGA de-burring countersink tool produced a clean finish with no chatter, unlike multi-cut countersinks.